Chemical mechanical grinding is also known as chemical mechanical planarization or chemical mechanical polishing (CMP). During semiconductor manufacturing process, surface planarization is an important technique for processing high density photolithography. In the process of surface planarization, controlling the uniformity of the wafer surface is very important because only a planarized surface without height variation may avoid scattering of light during the exposure process. In addition, uniformity of wafer surface may also affect electrical parameters of electronic devices. Specifically, uneven thickness of a wafer may lead to variation in the performance of the devices that are ultimately formed on the same wafer, thus may affect product yield.
With the development of semiconductor manufacturing technology, CMP is regarded as the only processing technology at present that can provide both global and local planarization. The CMP technology has been widely used to remove and planarize interlayer dielectric layer, metal layer (such as tungsten plug, copper connection line, etc.), and shallow trench isolation structure, etc. The CMP technology has become one of most rapidly developed technologies for semiconductor manufacturing processes.
FIG. 1 shows a schematic view of an existing chemical mechanical polishing apparatus.
Referring to FIG. 1, the chemical mechanical polishing apparatus may include a polishing platen 01 and a polishing pad 11 placed on the surface of the polishing platen 01. The chemical mechanical polishing apparatus may also include a wafer holder 02 to hold a wafer S which needs to be planarized. The chemical mechanical polishing apparatus may further include a dropper 30 to introduce polishing fluid 31. The wafer holder 02 and the dropper 30 may both be disposed above the polishing platen 01.
The wafer S to be planarized may be held on the surface of the wafer holder 02. The surface of the wafer S to be polished may face to the polishing platen 01 and may be in contact with the polishing pad 11. The wafer holder 02 may ensure that the wafer S is pressed against the surface of the polishing pad 11.
During the chemical mechanical polishing process, relative movement between the wafer holder 02 and the polishing platen may be achieved by driving the wafer holder 02 and/or the polishing platen 01. In the meantime, the dropper 30 may introduce more polishing fluid 31 onto the surface of the polishing pad 11. Therefore, utilizing the relative movement between the polishing pad 11 and the surface of the wafer S as well as the chemical reaction between the polishing fluid 31 and the surface material of the wafer S, a portion of the surface material to be polished may be removed so that the surface to be polished may be planarized.
As described above, the polishing pad may be directly in contact with the wafer, thus the properties of the polishing pad may directly affect the performance of the wafer polishing process. Moreover, the polishing pad is a consumable component in the chemical mechanical polishing apparatus. That is, each polishing pad may have a service lifetime. However, precisely determining the service lifetime of polishing pads fabricated by existing methods may be very difficult, thus the quality of polished wafers may be affected when the service lifetime is not properly determined.
The disclosed polishing pad, monitoring method, and monitoring system are directed to solve one or more problems set forth above and other problems in the art.